gypcrete and floor drains

[akbmunsell]

Hi everyone
Its been a cold building season here in Alaska, but at least our days are finally getting longer. Its not quite as easy to work from sun up to sun down as it was last month when we only had about 5 hours of dayligt.

I have a question that I can’t seem to find a answer to. I’m getting ready to have gypcrete poured over radiant tubes and I can’t figure out how to put a floor drain in the laundry room and have it work with the gypcrete. I have looked and searched all over this site and the internet in general. I have asked my plumber, who suggested a regular two part drain but didn't have any idea how to use it and even asked at the local plumbing supply house, but I haven't really got a good answer.

The gypcrete will be a 50/50 mix of regular gypcrete and gypcrete 2000, as recommended by the installer. I will be using a sleeper system for most of the house for nail down hardwood, but the bathrooms and laundry room will be tiled. In tiled areas the gypcrete will be sealed with the Maxxon Overspray primer/sealer, again as recommended by the installer.

One option would be to treat the floor like a shower floor, leave out the gypcrete and install a slightly sloping mud bed and use a Kerdi Drain (which I haven’t used yet, its new technology since I last did mud bed showers).

Another option would to leave a circular hole in the gypcrete around the drain and then install a two piece drain with a mud bed packed around it. Then the lower part of the drain could be sealed using the Noble Companies NobleFlex Drain Flashing and the rest of the floor waterproofed with a sheet membrane or liquid.

What other options do I have? Any ideas?

[David Meiland]

Re: gypcrete and floor drains

With a few caveats, this seems like a good place for a Kerdi drain. You want the gyp to stay totally dry--this is not a situation for a typical shower drain because that assumes a top layer of mud that can get wet under the tile. IF you can determine that there is a good way to bond the Kerdi to the gyp, you may have a winner. I would talk to Schluter, and also to Laticrete, see what they can tell you.

The other questions would be about slope to the drain, and about a trap primer since the drain won't get used much....?

You could also talk to the gyp sub about using a different material in the tile areas... lightweight concrete or even just regular concrete with a flow additive. Might be an easier deal if the pour is not moisture sensitive, and tiling it might be easier too.

[mbyrne]

Re: gypcrete and floor drains

Some Gyp-crete products are the very last thing you want to use under tile. I would get a written performance statement from your installer that the Gyp-crete you are going to buy is rated for use with both radiant heat and with tile (and I see no sense whatsoever in using a poured gypsum product that requires the addition of a membrane to "complete" the performance of the SLU.

Maxxon has a product specifically made for tile, or you can by SLU-for-tile from a supplier like Custom or Mapei, and have your local Gyp-crete guy pump it for you.

Suggestion: dam the shower area and after the SLU pour has cured, strip away the temporary dam and slope-float the shower.

[Kgphoto]

Re: gypcrete and floor drains

Is this a floor drain that is going to see regular usage, like in a shower, or just one for the rare emergency?

If the former, then treat the floor as a shower pan and Kerdi is the way to do, especially if you don't do this often. Much easier to work with than standard liners.

Tile does not get set on gypcrete without a membrane between it and in the Schluter (Kerdi) line, that would be DITRA.

[David Meiland]

Re: gypcrete and floor drains

Tile does not get set on gypcrete without a membrane between it and in the Schluter (Kerdi) line, that would be DITRA.

But which drain would you use with Ditra?

[akbmunsell]

Re: gypcrete and floor drains

Thanks for the input. I realize that there are challenges with putting tile on gypcrete, but as David asks, if the challenges are met with Ditra, what drain would you use? The typical two part drain doesn't seem to fit unless you use the Noble product, but then what would it take to install the drain and get the gypcrete poured. On the other hand, if the Kerdi Drain is used, what would that take, suspend the Kerdi Drain and pour the gypcrete around it, or make up a plug shaped like the Kerdi Drain and pour the gypcrete around that?

Its almost funny just how many different opinions there are about how to put radiant heat in a suspended floor. The normal go to guys, the pro plumbers and heating people push tubing, gypcrete and boilers, which is pretty expensive, probably the most expensive, while others who seem to have done a lot of research and have web sites, push other systems and stay away from gypcrete completely.

I just know that I have a gypcrete installer coming next Wednesday and I need to have all the holes in the floor plugged. I also have sheetrock hangers scheduled for the following Monday, so I would really like to have all the heat tubes covered up with something.

have a good night

[Kgphoto]

Re: gypcrete and floor drains

Ya know, I am going to have to look up that detail. Before I do, I am going to venture a GUESS that my common sense tells me would be the way.

You seal the seams of Ditra with a piece of Kerdi Band. So I would do the whole floor with Ditra and then set the drain so it finishes flush with the Ditra and then make a collar with Kerdi Membrane.

Now DON"T go ahead and do this until I check my sources.

Normally you would just use the Ditra out in the area that is the floor of the bathroom and Kerdi the shower stall area as that part of the floor wouldn't get all that wet.

In your situation you MAY have to overlap all the Ditra with Kerdi, if the floor gets repeatedly wet. The ditra would provide the uncoupling function and the Kerdi more the water proofing.

[Robert Z]

Re: gypcrete and floor drains

Some Gyp-crete products are the very last thing you want to use under tile. I would get a written performance statement from your installer that the Gyp-crete you are going to buy is rated for use with both radiant heat and with tile (and I see no sense whatsoever in using a poured gypsum product that requires the addition of a membrane to "complete" the performance of the SLU.

Maxxon has a product specifically made for tile, or you can by SLU-for-tile from a supplier like Custom or Mapei, and have your local Gyp-crete guy pump it for you.

Suggestion: dam the shower area and after the SLU pour has cured, strip away the temporary dam and slope-float the shower.

This is great advice....I know of some LEGENDARY gypcrete failures here in the DC area....and in one building where we worked, they tore out a redid the gypcrete 3-5 times in certain condos. You would think that after the first one or two times they would have learned something. :)

As MB said, be sure that the product you are using is suitable for ceramic tile.


You could use a liquid membrane with a clamping drain, although you should check with the mfr to see if their product is compatible with gyprete. Custom and others have details for how to do this on their websites.

I know it would be more expensive, but less risk over all...but did you consider deck mud over all of the tubes rather than gyprete?

[inkster]

Re: gypcrete and floor drains

I would go with the Nobleseal bonded down with their adhesive to avoid the use of thin set and gypsum together.The drain flashing would allow you to use a clamping ring drain.